The present invention relates generally to disc recorder drives and more particularly to a direct coupled disc recorder drive employing a brushless DC motor and an arrangement for packaging the same.
This application is an improvement of the disc recorder disclosed in the following related cases assigned to the same assignee. DISC FILE ASSEMBLY, U.S. Pat. No. 4,092,687; DRIVE SPINDLE ASSEMBLY FOR DISC FILE, U.S. Pat. No. 4,101,945 and COMBINED SPEED CONTROL AND SECTORING INDEX FOR DISC RECORDERS AND THE LIKE, filed Apr. 21, 1977, Ser. No. 789,528. The disclosures of these related applications are incorporated herein by reference. These three related cases disclose a disc recorder of the type having a direct coupled recording disc platform and motor with the recording disc platform mounted in a sealed enclosure. The recording disc platform includes an impeller for recirculating air through the enclosure both for cooling the spindle drive assembly and for aerodynamically flying the recording heads above the recording disc.
In direct coupled motor and spindle constructions of this type, the brushes used in the drive motor and the contacts in the shaft grounding arrangement will inherently produce small conductive dust or dirt particles as the brushes or the grounding contacts degrade through use. An accumulation of even a small amount of such particles on the recording disc or the recording heads will seriously impair the quality of recording and playback and must be prevented if at all possible. This can be a particular problem in disc recorders of the present type employing an impeller for circulating air within an enclosure for cooling the drive spindle assembly and aerodynamically flying the recording heads. If the direct coupled shaft extending from the enclosure to the motor is not effectively sealed, debris from the motor may be drawn upwardly along the spindle and impelled outwardly directly over the recording disc. This action is aggravated by the fact that the impeller vanes create a low pressure region at the bottom portion of the spindle shaft directly above the area of the motor and shaft seal. Although the sealing measures taken in prior art were generally satisfactory, in the event of seal deterioration, motor debris was carried into the recorder enclosure and the quality of recording suffered.